Do tele-converters keep the same minimum focus? Like if I have a 200mm that focuses to 1.3M, if I add a 1.4X teleconverter, will this result in a 280mm lens that still focuses to 1.3M? [I realize one loses one stop of speed, and likely some (quite a lot?) of sharpness.] How bad really is the sharpness degradation? OK if stop down fa few stops?